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首页> 外文期刊>Journal of Experimental Botany >Development and verification of a water and sugar transport model using measured stem diameter variations
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Development and verification of a water and sugar transport model using measured stem diameter variations

机译：使用测得的茎直径变化开发和验证水和糖的运输模型

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In trees, water and sugars are transported by xylem and phloem conduits which are hydraulically linked. A simultaneous study of both flows is interesting, since they concurrently influence important processes such as stomatal regulation and growth. A few mathematical models have already been developed to investigate the influence of both hydraulically coupled flows. However, none of these models has so far been tested using real measured field data. In the present study, a comprehensive whole-tree model is developed that enables simulation of the stem diameter variations driven by both the water and sugar transport. Stem diameter variations are calculated as volume changes of both the xylem and the phloem tissue. These volume changes are dependent on: (i) water transport according to the cohesion-tension theory; (ii) sugar transport according to the Munch hypothesis; (iii) loading and unloading of sugars; and (iv) irreversible turgor-driven growth. The model considers three main compartments (crown, stem, and roots) and is verified by comparison with actual measured stem diameter variations and xylem sap flow rates. These measurements were performed on a young oak (Quercus robur L.) tree in controlled conditions and on an adult beech (Fagus sylvatica L.) tree in a natural forest. A good agreement was found between simulated and measured data. Hence, the model seemed to be a realistic representation of the processes observed in reality. Furthermore, the model is able to simulate several physiological variables which are relatively difficult to measure: phloem turgor, phloem osmotic pressure, and Munch's counterflow. Simulation of these variables revealed daily dynamics in their behaviour which were mainly induced by transpiration. Some of these dynamics are experimentally confirmed in the literature, while others are not.
机译：在树木中，水和糖通过液压连接的木质部和韧皮部导管运输。同时研究两种水流很有趣，因为它们同时影响气孔调节和生长等重要过程。已经开发了一些数学模型来研究两种液力耦合流的影响。但是，到目前为止，这些模型都没有使用实际的实测数据进行过测试。在本研究中，开发了一个综合的全树模型，该模型能够模拟由水和糖的运输驱动的茎直径变化。茎直径的变化是根据木质部和韧皮部组织的体积变化来计算的。这些体积变化取决于：（i）根据内聚张力理论的水传输; （ii）根据蒙克假设进行的糖运输; （iii）装载和卸载糖; （iv）不可逆转的由动力驱动的增长。该模型考虑了三个主要的区室（冠，茎和根），并通过与实际测得的茎直径变化和木质部树液流速进行比较进行了验证。这些测量是在受控条件下在年轻橡树（Quercus robur L.）树上和在天然森林中对成年山毛榉（Fagus sylvatica L.）树上进行的。在模拟数据和测量数据之间找到了很好的一致性。因此，该模型似乎是现实中观察到的过程的现实表示。此外，该模型能够模拟几个相对较难测量的生理变量：韧皮部膨大，韧皮部渗透压和蒙克逆流。这些变量的模拟揭示了其行为的日常动态，这主要是由蒸腾作用引起的。这些动力学中的某些已在文献中通过实验得到证实，而另一些则没有。

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